Molding sand



March 27, 1962 K. AQ MIERICKE MOLDING SAND Filed April 11, 1960 OON iSdHimmels Nolssaadwoo INVENTOR. KURT A. MIERICKE AGENT 3,027,265 MOLDINGSAND Kurt A. Miericke, Clarendon Hills, Ill., assignor to National LeadCompany, New York, N.Y., a corporation of New Jersey Filed Apr. 11,1960, Ser. No. 21,413 5 Claims. (Cl. 10G-38.2)

This invention relates to molding sands such as are -used for thecasting of metals, and more particularly to molding sands which arebonded with materials other than ordinary clay as such, and liquidsother than water.

In casting metals into a sand mold, the sand is commonly bonded withsmall Iamounts of clay moistened with water. Originally, sands were usedwhich contained naturally occurring clay, but in recent decades thepractice has arisen of adding specially selected clays to sands,particularly to sands which have been washed free of any clay or othercontaminating material. The composition and use of such molding sands inthe foundry art are well-known and will not be described further herein,except by reference to the literature, and in particular such monographsas Metal Castings, by Harry L. Campbell, New York, 1936; and the U.S.Navy Bureau of Ships Foundry Manual, Bulletin No. Navships 250- 0334,Washington, D C., no date.

The properties of conventional molding sands such as have been describedleave much to be desired, in spite of their wide and universal usage.Many problems arise from the fact that the properties of theconventional molding sands depend greatly upon their moisture content.Slight variations in moisture content can cause radical changes in theircompressive strength, permeability, and flowability. These changes, ifuncorrected, will cause surface and interior defects in castings andresult in substantial scrapping. The moisture content of molding sandscan vary `appreciably during pouring, working, or storing, as a resultof evaporation losses. Very little can be done to prevent theevaporation of water because of its relatively low boiling temperature,necessitating frequent and delinite additions of water to the sand.

Conventional molding sands must be quite permeable, that is, must passgas freely, in order to accommodate the large volume of water vaporevolved when the metal is poured. Since permeability is a function ofpore diameter, which, in turn, is a function of average sand particlesize, a definite lower limit is set on the fineness of sand which can beused in any particular type of casting, so that it is seldom possible toobtain as smooth a surface finish as desired when using conventionalmolding sands, because very line sand cannot be used because of its lowpermeability.

Another factor influencing the smoothness of surface finish is theadherence or even bonding of sand particles to the metal, alter thecasting process has been completed. This quite common occurrence makesit necessary to clean up castings, as by sand blasting, wire brushing,grinding, and the like, so that a clean metal surface is presented bythe casting, instead of one marred Vby sand grains and other tightlybonded residue from the face of the sand mold. The cleaning time andcost involved can be an appreciable portion of the total cost of thecasting.

In order to avoid the disadvantages of sands containing water, manywater-free molding sands have been tried in foundries over the years.These water-free sands contained oil as a `bonding agent. Oil wasbelieved to be superior `to water because it boiled at a highertemperature than water and evolved less gas, thereby requiring less sandcontrol because of lower evaporation losses. The oil also caused lesschilling of the molten metal. In spite of these advantages, the oil-sandsytsems were `always found to be impractical because of their very lowbond strength.

The proposal has `been made to thicken the oil in systems of the typedescribed with bentonite which has been made organophilic by treatmentwith certain organophilic materials. Alternatively, the proposal hasbeen made to incorporate with the oil in such systems a clay known asattapulgite, yalthough not previously placed in an organophilic state.There are certain disadvantages connected with both of these ratherrecent proposals, which the present invention avoids.

An object of the present invention is to provide a molding sandsubstantially free `from water, and, hence, not subject to waterevaporation losses.

Another object of the present invention is to provide a molding sandcontaining a bonding agent which is effective in an essentiallynon-aqueous lubricant vehicle.

Another object of the present invention is to provide molding sandcompositions of such character that sand grain fineness can be muchsmaller than possible with conventional clay-water bonded sands, thusleading to the production of smoother castings.

Another object of the present invention is to provide a molding sand ofsubstantially lessened adherence to castings formed therein, thussimplifying the problem of cleaning the castings from residual sand.

A further object of the present invention is to provide a molding sandexhibiting the superior properties obtainable with organophilcattapulgite produced in accordance with the invention.

Other and further objects of the invention will become apparent as thedescription thereof proceeds.

I have discovered that a satisfactory molding sand of improvedproperties can be obtained by using (n) sand which is bonded with aminor proportion of (b) organophilic attapulgite as hereinafter moreparticularly described and (c) a minor proportion of a liquid lubricantof non-aqueous and generally organic character. Optionally, I mayinclude in the mix additionally (d) a finely divided, inert material ofpowdery character, and/or (e) an additive having the power of especiallyactivating the grease thickening agent so as to increase its thickeningor gelling characteristics in the particular lubricant used. Over andabove these, l may optionally also add (f) other materials known to themolding sand art such as gelatinized starch and starchy flours, powderedgilsonite, powdered ltar, lignosulfonate compounds, `and the like.

The several components of the complete molding sand composition aremixed together by means well-known in the art, some of which will bealluded to in the examples which follow. The sand component will ingeneral be by far the largest in percentage by weight of the totalcomposition, generally from 85% to 98% thereof, While the otheringredients are used in relatively small percentages in the order of afew percent by weight of the total ingredients, as again will be morecompletely detailed hereinbelow.

(a) THE SAND COMPONENT The sand most commonly used in molding sands, and

that which I prefer for general use and for the production of what maybe termed an all-purpose molding sand composition, is a relatively puresilica sand. Such sands are available from a number of suppliers, andmay be furnished in a considerable range of particle sizes and particlesize distributions. The invention is not limited to the use of anyparticular particle size of sand, nor indeed to the type of sand used.For special work, particularly where very high temperatures areconcerned, Zircon sand may be used, and has been found to work very Wellin compositions made up in accordance with the invention. Olivine sandis likewise highly usable, and is preferred in Some installationsbecause of its freedom from any silicosis hazard in use. Other sands maylikewise be used.

(b) THE ORGANOPHILIC ATTAPULGITE It is known that it is possible toconvert a certain clay known as attapulgite to an organophilic state inwhich the converted compounds have the property of thickening or gellingorganic liquids, by treatment with a suitable organic compound in such away that the surface of each colloidal particle of attapulgite iscovered with an organic compound having as at least part of its moleculean organophilic, oleophilic, hydrophobic portion, such as a longhydrocarbon chain, an abietyl radical, or the like. Attachment of theorganic compound (which may be termed organophilogenic, since it impartsorganophilic character to the silicate in question) to the attapulgiteparticle may be by metathesis. It is generally most convenient tofurnish the organophilogenic agent in the form of an organic cationwhich can be exchanged for the exchangeable cations normally present onthe attapulgite.

A general procedure for forming organophilic organictreated attapulgiteis set forth in detail in Hauser Patent No. 2,531,427, the disclosureand teachings of which are made a part of this specication by referencethereto. The Hauser patent just mentioned set forth a number of possibleclays, among which is attapulgite. Attapulgite is a clay mineral havingsubstantial base-exchange capacity and particularly obtainable innorthern Florida and southem Georgia. It is particularly effective if ithas been freed of non-colloidal material, and to some extentmechanically dispersed by wet beneciation including centrifugation priorto reaction with the chosen organophilogenie agent. Attapulgite isavailable from a number of suppliers, under such trade names as Zeogeland Floridin.9 A suitable purified attapulgite is available under thetrade names of PermageL and AttageL Various organophilogenic compoundsmay be used with attapulgite. A particularly effective organophilogenicagent for use with purified attapulgite is Victamine C, which is thetrade name for a cationic agent manufactured and sold reportedly underUnited States Patent No. 2,406,423, and having the following chemicalformula, where R is a water solubilizing group:

It has been found advantageous to use in conjunction with Victamine C anadditional organophilogenic agent such as that commercially availableunder the trade name of Ethomeen 18/ 15, which is a tertiary amine inwhich a stearyl radical is bonded to the nitrogen atom together with twopolyoxyethylene groups each representing the polymer of approximately vemoles of ethylene oxide likewise bonded to the nitrogen atom. These twocornpounds may be used in the proportion of about 16% of Ethorneen 18/15and 10% Victamine C based on the weight of the purified attapulgite.

The reaction, leading to the production of an organophilicorganic-treated attapulgite material, may take place separately, thatis, before the product is added to a molding sand mix; or the reactionmay be caused to take place by commingling the organophilogenic compoundand the attapulgite in the molding sand mix itself, or at anintermediate stage thereof. For example, if the organophilogeniecompound is dodecyl ammonium chloride, the latter may be reacted insubstantially stoichiometric proportion, as taught in the Hauser patentnoted, so as to form a dodecyl ammonium attapulgite. Alternatively, thedodecyl ammonium chloride may be added separately to the mixture of sandand liquid lubricant in the muller used to produce the iinal moldingsand mix, of course together with any optional additional ingredients.Again, the attapulgite and the dodecyl ammonium chloride can be added tothe liquid lubricant and then this mixture added to the molding sand inthe muller. Such commingling of the organophilogenic compound and theattapulgite will result in the production of the organophilicorganictreated attapulgite material desired; the reaction is of courseaided by heat and time, so that when the reactants are added separatelyas in the example just given, a few minutes extra mulling time should beallowed for the completion of the metathesis reaction in comparison tothe mulling time allowed where the organophilic organictreatedattapulgite material is purchased as such, already formed, or otherwisemade up ahead of time, and added as such to the sand mix in the mulleror other sand mixing mechanism.

(c) THE LIQUID LUBRICANT The liquid lubricant forming an importantcomponent of the molding sand compositions of the present invention maybe chosen from a Wide variety of non-aqueous liquids of substantial oreven slight lubricating properties and of generally, although notnecessarily always, organic character. I prefer ordinary lubricatingoil, for example, coastal stock SUS at 100 F., 24 A.P.I., but theinvention is capable of being carried out successfully with many otherliquids, such as, for example, kerosene, other hydrocarbon liquids oflubricating character about equal to kerosene or substantially greaterin lubricating properties, such as medium and heavy petroleumlubricants, hydrogenated aryl compounds such as decahydronaphthalene,chlorinated naphthalene and the like, A resume of the more importantbroad groupings of suitable liquid lubricants which can be used is asfollows:

Hydrocarbons Kerosene Diphenylethane, asymmetrical Mineral lubricatingoil Decahydronaphthalene Diesel Oil Liquid polybutylene H alogcnatedHydrocarbons Hexachlorobutadiene Eslers Dioctyl sebacate Hydrogenatedsoya oil 2-ethylhexyl sebacate Linseed oil Dioctylphthalate Soya oilDibutylphthalate Maize oil Tricresyl phosphate Jojoba oil Hydrogenatedcottonseed oil Sperm Oil Other "Synthetic Lubricants Water-solublemonoalkyl ethers of oxyethylene-oxy-l, 2 propylene copolymers (availableas Ucon lubricants).

Silicon Derivatives convenient listing of liquid lubricants which may beused in the present invention occurs in Patent 2,625,508, Acolumn 6,line 23, to column 8, line 44. Reference may be made to this listing foradditional liquid lubricants, and this portion of Patent No. 2,625,508is hereby incorporated in this specification by citation. Additionalinformation on the silicon derivatives which are also useful liquidlubricants for the purpose of this invention may be obtained in Chapter4 of the book An Introduction to the Chemistry of the Silicones, by E.G. Rochow, First Edition, New York, 1946; and chapters 5 and 6 of theSecond Edition of this same book, New York, 1951.

It will be further understood that the liquid lubricant need be liquidonly at the lower working temperatures involved. For example,hydrogenated cottonseed oil is a solid iat 70 F., but liquefies atsomewhat below about 100 F., which is a temperature readily obtained inthe mulling operation and, indeed, maintained in normal foundry Workwhere recycling of the molding sand is carried out.

(d) THE OPTIONAL FINELY-DIVIDED ADDITIVE I have found that in some casesit is advantageous to add a relatively small amount of a generallyinert, finelydivided material of particle size twenty to one hundredtimes yor more smaller than the particle size of the sand componentused. For example, ordinary commercial iron oxide, substantially all ofwhich passes a 325 mesh A screen, is suitable and is preferred since itis commercially available at relatively low cost and is quite inert. Theiron oxide may be hematite or a less highly oxidized form such asmagnetite. Silicon flour, of 250 or 400 ing sands of the conventionalwater-clay-sand type, it is frequently advantageous to use relativelysmall amounts of extraneous materials, such as gelatinized starch andstarchy flours, powdered gilsonite, powdered tar, ligno- Sulfonatecompounds, and the like. Generally speaking, such of these additives asare particularly adapted to a water system, such as lignosulfonatecompounds, for example, find relatively little use in the presentinvention. On the other hand, with certain classes of castings, ofcourse, it may in some cases be found advantageous to use additives ofthis optional and rather miscellaneous category, and such are thereforewithin the broad purview of the invention. Such of these materials asare inherently compatible with an oil system will be found preferable,when it is felt that such additional additives need be used. These are,for example,l powdered gilsonite, powdered tar (especially coal tar),comminuted air-blown asphalt, hydrogenated c-astor oil, carbon black,lamp black, wood flour, and the like.

Relative Proporfions of the Components tities of organophilicattapulgite and lubricant are best mesh, may be used, as may likewisethe commercial silica flour known as 800 mesh silica. Other silicates,ground barite, and the like can also be used, as the particle size isgenerally less than about 325 mesh, although feldspur, barite, syntheticzeolite fines and the like are not as desirable as silica or iron oxidesince the former tend to ux at relatively low temperatures, which is notthe case with silica or iron oxide. Finely-divided Zircon andfinely-divided alumina may be used with good results, except that theseare considerably more expensive than either iron oxide or silica flour.As has been mentioned, these are purely optional additives, and theinvention may be carried out without their use at all.

(e) THE OPTIONAL ACTIVATING ADDITIVES The organophilic organic-treatedattapulgite materials,

when used with some of the liquid lubricants within the scope of theinvention, will often give even better results from the standpoint ofthickening or gelling the liquid concerned if a relatively small amountof an activating additive is used in conjunction with the treatedattapulgite. Relatively small amounts of additives characterized bybeing of relatively low molecular weight and relatively high dielectricconstant such as water, ethanol, methanol, acetone, propylene carbonate,and the like, will enable a reduction to be made in the total amount `ofthe organophilic attapulgite necessary to achieve the same result ascompared in the case when an additive is not used. In general, inaddition to organic liquids having a dielectric constant of more thanl0, liquids having an electric moment between l.2 l018 and 2.8 l018electrostatic units are suitable. Of such compounds, I prefer methanol,since it is effective, readily available, and inexpensive. The fact thatsuch additives as have been described are relatively volatile does notat all preclude their use in accordance with the invention. Activatingadditives of the type just described, i.e., liquids having a dielectricconstant of more than l0 or an electric moment between 1.2)(10-1s to 2.810-1B electrostatic units will be termed polar additives herein and inthe claims which follow.

(j) OTHER OPTIONAL ADDITIVES It is well-known that in the art yofcompounding moldl, properties to molding sand compositions.

considered together, since in a given composition if a ylarger amount ofthe former is used in general it will be found necessary to increase theamount of liquid lubricant proportionately. This is understandable inview of the fact that the organophilic attapulgite combines mechanicallywith the liquid lubricant, and the two together form a compositionhaving the nature of a sticky paste. .In general, the ratio oforganophilic attapulgite to liquid lubricant will be much greater thanthe ratio of the former to a given lubricant when the two are compoundedin the manufacture of lubricating grease. For example, in thelubricating grease art, it is usual to employ from 5% to perhaps 20% byweight of grease-thickening agent per total weight of grease. I havefound that greases `of this conventional type do not impart suitablemolding Rather, in carrying out my invention, I use more nearly equalamounts of organophilic attapulgite and lubricant, although these may bevaried within rather wide relative limits. This is particularly so inView of the fact that different lubricants differ among themselves inthe amounts necessary to impart plastic consistency to a given grease.Generally, however, it may be stated that the ratio of organophilicattapulgite to liquid lubricant is within the range of 1:1 to 2:1, thatis, the former will outweigh the liquid lubricant. A representativerange of percentages of the organophilic attapulgite is from 1% to 5%based on the total weight of the molding sand composition, but in somecases both of these limits may be exceeded. A representative range ofpercentages of liquid lubricants is from 1/2% to 4% by weight of totalmolding sand composition, but here again it will be understood that bothof these limits may be exceeded.

When an optional finely-divided additive is used, such as, for example,powdered iron oxide or silica flour, the amount to be used is subject toconsiderable variation. In the first place, none at all need be used,although it is found that an increase in both hot and green strength ofthe molding sand is generally brought about by the use of smallquantities of the aforesaid finely-divided material. If too much of thefinely-divided material is used, it tends to reduce the permeability ofthe sand, and is in general wasteful, as it tends to absorb liquidlubricant and thus leads to the employment of a wasteful excess ofliquid lubricant. It will. be found that with average mixes,approximately 1% by weight of iron oxide or silica iiour based on thetotal weight of the composition will be suitable, although quantities offrom to 2% by total Weight will still give workable molding sandcompositions in most of the cases.

The optional activating additive may in general be used to obtaingreater yield from the organophilic organic-treated attapulgite.Representative additives of this class have been described hereinabove;it is to be expected that they will diifer among themselves in theamount which needs to be added for a given degree of activation orotherwise stated as a given degree of increase of thickening or gelationpower of the organophilic attapulgite. In general, the quantity to beadded will be of the same order of magnitude as the organophilicAattapulgite itself, and more particularly, in general from about 50% to100% of the weight of the latter. It is believed that activatingadditives of this type act by adsorption in the organophilicattapulgite-lubricant complex, so that it will be readily understoodthat an excess, for example, twice the optimum quantity, representsmerely a waste and contributes material to the molding sand mix which ingeneral will be ashed off at relatively high temperatures. On the otherhand, using too little of the optional activating additive willrnereparticularly suitable in carrying out the invention is to use amuller, for example, a Simpson Intensive mixer, pour the desired amountof sand into a clean dry muller, start the machine, allow it to makeseveral revolutions to mix the sand, then add all the dry agents, suchas, for example, the organophilic attapulgite and any other dryadditives, mix for one to two minutes, depending upon the size and typeof mixer and the load therein, and then add the liquid lubricant and anyother liquid additives. Mulling is continued for an additional length oftime suiicient to produce a homogeneous sand mix. This time may be aslittle as ten minutes more, but may in some cases-be as long as thirtyminutes. It Will be appreciated that a dispersion of the organophilicattapulgite in the liquid lubricant takes place, or otherwise viewed, anadsorption of the liquid lubricant into the organophilic attapulgitetakes place, and this is a process which takes some time, and in generaltakes a longer time for large particle size of the organophilicattapulgite granules or powder and high viscosity of the liquidlubricant, and conversely takes a shorter time when the former is veryfinely comminuted, and also with liquid lubricants of relatively lowviscosity.

A number of examples of the employment of the invention in compoundingmolding sand mixes will now be given.

EXAMPLES Table I Hot Strength, p.s.i.

Gr. Impact Dry No. Content (percent) 1,500 F. 2,000 F. Str. Perm. Flowa-Def. at Comp., Sand (p.s.i.) bility p.s.i.

Blows 2 4 6 2 4 Min. Miu. Min. Min. Min.

VV...-.. 64 81.5 85 65.5 45 4.6 14.3 84 5 15 9 6 We. 10.

WW 19 27.5 37 19.5 20 9.7 18.7 81 11 10.8 We. 101.

zz 439 11.1 23 s6 14 We.10.

1 Sand preheated to about 190 F. 2 1400 F., 12 minutes. 3 1600 F., 12minutes. 4 2000 F., 12 minutes.

ly have the effect of reducing the efficacy of the organophilicorganic-treated attapulgite so that more of it will have to be used.Again, where an optional activating additive is used, it will be foundthat the optimum amount for use will vary with the type of lubricantchosen. It is best, therefore, to determine the amount of optionalactivating additive, if any, to be used by making a few preliminarytests with the mixture of the actual components at hand.

When other optional additives are used, their quantity will in generalbe small. As a matter of fact, they are not necessary for the productionof a workable molding sand composition in accordance with the presentinvention, but may be used for special effects. In general, they willnot be used in quantities of more than 1% or 2% of the total mix.

The method of mechanically compounding the.var ious components into amolding sand composition in general follows standard practice. Theordinary foundry equipment for sand mixing and conditioning is Welladapted to the exercise of the present invention without any change ofequipment. Conventional mixing equipment in use in American foundries isalluded to in chapter 4 of the U.S. Navy Bureau of Ships Foundry Manualhereinbefore cited. A practice which has been found In the aboveexamples, the identifying letter for the individual mix is given in theiirst column, while in the second column are given the several additivesto the sand whereby the molding-sand mixture is formed. Theseingredients are in some cases abbreviated in the table above, theabbreviations used being given below. The sand used appears in the lastcolumn, again abbreviated as explained below. The various properties ofthe molding sand compositions of the several examples are set forth inthe intermediate columns. In the columns headed Hot Strength, a 11/8inch diameter by 2 inch long specimen was prepared with a Dietert No.754 sand rammer and the compressive strengths at the elevatedtemperatures and after the period of time shown in the various columnswere determined with a Dietert No. 753 Thermolab, these being well knowntesting apparatuses in American practice. The hot strengths are given inpounds per square inch. The green strength test was performed on 2 inchspecimens rammed with a Dietert No. 315 sand rammer, and measured with aDietert No. 401 compression instrument. Dry compression strength wastested on this equipment as well, after drying at 220 to 230 for onehour. Permeability was measured with a Dietert No. 320 permeabilitymeter with a standard 1.5 mm. orifice. Flowability was measured by aDietert No.

730 owability indicator attached to a Dietert No. 315

sand rammer, and the impact properties were determinedV O.A.:Organophilic attapulgite made by reacting commercialdimethyldioctadecylammonium chloride as Arquad 2 HT with attapulgite inthe proportion of 35 milliequivalents of the quaternary compound per 100grams of the attapulgite.

FeO: Commercial iron oxide, 95% minus 325 mesh,

largelyhematite.

M.A.: Commercial methyl alcohol.

Eth. 18/15: Ethomeen 18/15, chemical composition given hereinabove.

Vic. C: Victamine C,l chemical composition given hereinabove.

Coast. (C.R.): Lubricating oil, coastal stock, conventional rened,viscosity index'approximately 30, A.P.I. gravity 24.4.

We l: Washed silica sand sold as Wedron No. 10

sand, GFN (grain iineness number) 133.

Thus, for example, mix VV consists of 92.95 parts by weight of Wedronsand, 4 parts by weight of attapulgite, 0.65 part by weight of Ethomeen,0.4 part by weight of Victamine C, and 2 parts by weight of lubricatingoil of the type designated, the whole m-ix having been mulled in amuller for a time suitable for the appearance of the properties shown,which in general was about three (3) minutes.

'In order to show the extraordinary and unexpected differences andsuperiority of 'a molding sand mixture made with organophilicattapulgite as contrasted with an otherwise similar molding sand mixturemade with organophilic montmorillon-ite, the following tests wereperformed:

A molding sand mixture was made up in accordance with the formulation ofexample ZZ hereinabove. AS the data accompanying this example show, thissand was made up with Wedron silica sand, a coastal stock oil, ironoxide in the proportion of 0.4 part of iron oxide to each part oforganophilic attapulgite, and 0.5% methyl alcohol.

For purposes of comparison, an organophilic montmorillonite which hadbeen prepared in the same fashion as the organophilic attapulgite ofexample ZZ, except that montmorillonite was used instead oflattapulgite, was substituted in this control test. The organophilicmontmorillonite, hereinafter abbreviated as O.M., was a stoichiometricreaction product of dimethyldioctadecylammonium chloride withmontmorillonite, and thus in accordance with the base exchange capacityof the montmorillonite had 95 milliequivalents of the quaternarycompound per 100 grams of the montmorillonite. The ratio of iron oxideto organophilic clay was maintained the same as in example ZZ, thepercentage Aof methyl alcohol was the same, the sand was the same, andthe oil and O.M. percentages were adjusted to give as nearly as possiblethe same dry compression strength. The amounts found necessary -for thiscontrol were 2.5% O.M., and 2% oil.

The compression strength of the sands made up with the ltwo organophilicclays in the fashion described was then tested over a range oftemperatures from room temperature to 2600 F. It will be understood thatseparate samples were made up and heated in an oven for each test. Thecompression strengths obtained were as follows:

Compression Strength, p.s.i.

The compression strengths of the two sand mixes as a function oftemperature are plotted in the drawing. The results are startling, inthat .they show that over the range of room temperature to 400 F. theAtwo sand mixes are substantially alike in strength. At temperatures inexcess of 400 F. and over a wide range up lto somewhat greater than 2200F., the compression strength of the organophil-ic attapulgite mix ismuch greater than that of the O M. mix. On the other hand, at 2400 F.the compression strengths of the two mixes are substantially equal,

and if this temperature is exceeded, up to 2600 F., for

example, the compression strength of the organophilic attapulgite mixdrops while that of the O.M. mix increases.

The effects demonstrated by Ithese comparative tests are of greatimportance in casting technique, as mold washing is reduced for largemagnesium and aluminum casting, for example, when the organophil-icattapulgite mix is used because of the high compression strength overthe Wide temperature range just described. On the other hand, the lossof strength of the latter at the highest temperature shown, rather thanbeing a disadvantage, is an advantage, as it permits easier shake-outwhen gray iron and steel, for example, are cast.

lt will be appreciated that mulling time is greatly dependent upon thesize and type of the muller or other mixing equipment used, and the sizeof the batch being mulled in relation to the capacity of the muller.Accordingly, optimum mulling time is best determined by an actual teston the batch in question and with the equipment at hand.

Throughout the specification and claims, quantities of additives presentin the molding sand compositions in addi-tion to the sand itself areexpressed as percentages by total weight of the finished molding sandmixture, as is `clear from the example immediately hereinabove.

In general, a molding sand composition having a green strength of lessthan 2.4 pounds per square inch, as de termined by the standardprocedure of the American Foundrymens Society, is not a practicablemolding sand composition for casting purposes. While the percentages ofthe various ingredients are subject to great variation within the broadscope of the invention, it will be selfevident that if so little of thenecessary additives are present that the green strength of the finishedcomposition falls below substantially 2.4 pounds per square inch, thenthe composition is not properly termed a. molding sand compositionwithin the meaning of this specification.

It will be apparent that the invention is a broad one, and muchvariation of ingredients, quantities and procedure is permissible withinthe broad scope of the invention and of the claims which follow.

The distinction is to be noted between attapulgite, and attapulgitewhich has been caused to become organophilic by treatment as hereinabovedescribed. Attapulgite is a natural clay in which the ultimate particlesare acircular, (i.e., needle shaped) and, hence, there is a looseresemblance between attapulgite and very short iibered asbestos or likeasbestiform minerals. A iinely divided, needle-shaped mineral such asattapulgite or, for that matter, certain asbestos varieties, whenincorporated with various liquids is often able to confer somestructural viscosity on the system. An example is the incorporation offinely divided asbestos in paints in order tol give them more apparentbody. However, this is clearly to be distinguished from the peculiarproperty of an organophilic attapulgite in accordance with the inventionof forming a sticky gel With a liquid lubricant as hereinabove exempliedand described. The sticky gel produced when using organophilicvattapulgite inl accordance with the invention functions in a superiorfashion in forming molding sand compositions having desirableproperties, Whereas this is not the case if an ordinary attapulgite isused with a lubricating oil and a molding sand, for example.

This application is a continuation-impart of my co-pending `applicationSerial No. 537,069, filed September 27, 1955, now abandoned.

Having described the invention, I claim:

l. A molding sand composition, comprising sand, and `a binder consistingessentially of organophilic attapulgite,

and lan organic liquid lubricant exhibiting lthe propertyof gelling whenbrought into admixture with said organo philic attapulgite in a weightratio of between about one -and about ve parts of said organophilicattapulgite per part of said liquid lubricant.

2. A nonaqueous molding sand composition compris- 12 ing sand and abinder consisting essentially of organophilic attapulgite and of aliquid lubricant exhibiting the property of gelling When brought intoadmixture with said organophilic -attapulgite, said organophilicattapulgite and said liquid lubricant being present in proportions ofbetween about 1:1 and 2:1 relative to each other.

3. A molding sand composition consisting essentially of lfrom to 98% byWeight of sand, and from 2% to 15% of a mixture of organophilicAattapulgite and an organic liquid lubricant exhibiting the property ofgelling when brought into admixture with said organophilic attapulgite,said organophilic 'attapulgite and said liquid lubricant being presentin a Weight ratio of between about 1:1 and 2:11.

4. A molding sand composition according to claim 3, including from 0% to2% of a finely divided inert material of particle size 20 to 100 timessmaller than the particle size of said sand.

5. The composition in accordance with claim 3 wherein the organophilicattapulgite is a tetraalkyl quaternfary ammonium attapulgite.

References Cited in the le of this patent UNITED STATES PATENTS au NA

1. A MOLDING SAND COMPOSITION, COMPRISING SAND, AND A BINDER CONSISTINGESSENTIALLY OF ORGANOPHILIC ATTAPULGITE, AND AN ORGANIC LIQUID LUBRICANTEXHIBITING THE PROPERTY OF GELLING WHEN BROUGHT INTO ADMIXTURE WITH SAIDORGANOPHILIC ATTAPULGITE IN A WEIGHT RATIO OF BETWEEN ABOUT ONE ANDABOUT FIVE PARTS OF SAID ORGANOPHILIC ATTAPULGITE PER PART OF SAIDLIQUID LUBRICANT.